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I don't know how to look for the zone valves without digging up half my property. The previous (and original) homeowner (of 28 years) also had no idea when he sold me the house.

Suppose I am able to measure the current being drawn with my existing timer setup. What numbers am I looking for? In other words, in order to install a new controller what it the maximum current that my zones can draw in order for the new controllers to be compatible (and not produce the error messages you mentioend)?

Do I need to take the master controller into account as well?

What magnitude of current do today's solenoids draw vs. what mine might be drawing?

By the way, you might take a photo of your controller, with the bottom access panel removed, and post it here. Some of the Valets were configured so as to make exchanges fairly simple.

Sure, I could do that later tonight but I'm scratching my head as to why this would be considered relevant in finding a replacement timer.

Looking at some of your posts from 6-7 years ago, I see that you consistently recommend the Rainbird ICCs to replace the IV timers due to their ability to power the IV solenoids. Do they still make these timers (or equivalent)? Is there a list of timers that would be considered safe bets to power my solenoids? At this point it seems like the price tag of the controller is less of an issue than finding a compatible timer.

Suppose I go with a high power controller...and it turns out my solenoids are the newer ones the IV manufactured before going out of business (or even different solenoids altogether)...would this make my new timer not compatible?

When did IV go out of business? My house was built in '82. My neighbor's house has the same exact timer I discovered this weekend. Our houses are cookie cutters of each other for the most part.

Lots of times you will see near-identical sprinkler systems next door to each other. It just happens that the ones with Imperial valves are caught in a time warp.

Nifty method to determine AC current without needing an ammeter. Buy a one-ohm power resistor, of at least five watts rating, and connect it in series with the common wire to your zone valves. Then read the voltage across the resistor, when operating the sprinkler system. The reading, in volts, will equal the current, in amps.

Rather than taking photos of my timer I decided instead to make a quick 2 minute video demonstrating my attempt at following Wetboots' simplified procedure for measuring the current. I bought a 1 Ohm/10 watt resistor (10% tolerance) from Radio Shack and measured the voltage across it when a zone was turned on. I measured 0.2V on the 200V AC scale. Does that sound about right or did I do something wrong? Watch the video for yourself and see.

0.2 volts across the one-ohm resistor corresponds to a current of 0.2 amps, and that would indicate modern solenoids, and no issues with using any solid-state controller for a replacement.

The accuracy of this method depends on the precision of the resistor, and the accuracy of your voltmeter at the extreme bottom of its range. Since some of these meters could state "plus or minus two digits" or similar, when describing accuracy in detail, the values you measure may be more like ballpark figures. Still, if you were feeding two Imperial brass valves (master valve and zone valve) a current of more than an amp would be expected.

Good video. The setup was about what I'd have done. I remembered this shortcut from a long-ago exercise where the voltmeter was replaced by an oscilloscope, and the waveforms we observed were showing us the current in a circuit. You still might want to find an AC ammeter, to compare readings.

Of course, due diligence requires you get a reading for each zone, but I'd guess you're home free.